This invention relates generally to tissue-localizing devices and methods for their deployment and excision. More particularly, this invention relates to an improved tissue localizing device having an electrically energized locator element with ability to fixedly yet removably bound a tissue volume containing a region of interest, such as a nonpalpable lesion, foreign object, or tumor, preferably but not necessarily without penetrating that tissue volume. This invention also more particularly relates to methods for deploying that device and removing it with an enclosed and intact tissue volume.
Despite the advances made in technologies such as medical imaging to assist the physician in early stage diagnosis and treatment of patients with possible atypical tissue such as cancer, it is still often necessary to sample difficult-to-reliably-reach organ or tissue lesions by biopsy to confirm the presence or absence of abnormalities or disease.
One disease for which biopsy is a critical tool is breast cancer. This affliction is responsible for 18% of all cancer deaths in women and is the leading cause of death among women aged 40 to 55.
In the detection and treatment of breast cancer, there are two general classes of biopsy: the minimally invasive percutaneous biopsy and the more invasive surgical, or xe2x80x9copenxe2x80x9d, biopsy.
In the detection and treatment of breast cancer, there are two general classes of biopsy: the minimally invasive percutaneous biopsy and the more invasive surgical, or xe2x80x9copenxe2x80x9d, biopsy.
Percutaneous biopsies include the use of fine needles or larger diameter core needles. They may be used on palpable lesions or under stereotactic x-ray, ultrasonic, or other guidance techniques for nonpalpable lesions and microcalcifications (which are often precursors to metastatic cell growth). In the fine needle biopsy, a physician inserts a small needle directly into the lesion and obtains a few cells with a syringe. Not only does this technique require multiple samples, but each sample is difficult for the cytologist to analyze as the specimen cells are isolated outside the context of healthy surrounding tissue.
Larger samples may be removed via a core biopsy. This class of procedures is typically performed under stereotactic x-ray guidance in which a needle is inserted into the tissue to drill a core that is removed via vacuum aspiration, etc. Typically four to five samples are taken from the body. Examples of such stereotactic biopsy methods include the MAMMOTOME vacuum aspiration system by Johnson and Johnson of New Brunswick, N.J., the ABBI system by United States Surgical Corporation, Norwalk, Conn, and the SITESELECT system by Imagyn, Inc. of Irvine, Calif.
Open biopsies are advisable when suspicious lumps should be removed in their entirety or when core needle biopsies do not render sufficient information about the nature of the lesion. One such type of open biopsy is the wire localization biopsy.
After multiple mammograms are taken of the breast, the images are analyzed by a computer to determine the location of the suspect lesion in three dimensions. Next, after a local anesthetic is administered, a radiologist inserts a small needle into the breast and passes the needle through the suspect tissue. The radiologist then passes a wire with a hook on its end through the needle and positions the hook so that the end of the wire is distal to the suspect tissue. A final image is taken of the lesion with the accompanying wire in place, and the radiologist marks the film with a grease pencil to indicate the x-ray indicators of a suspicious lesion that should be removed. The wire is left in the tissue and the patient is taken to the operating room, sometimes hours later, where the suspect tissue is removed by a surgeon. The sample is sent to a radiologist to determine, via an x-ray examination, if the sample contains the indicators such as microcalcifications and if the sample size and border are adequate to confirm the removal of all suspicious tissue.
Examples of such wire markers are well known in the art. See, e.g., the following patents, each of which is incorporated herein by reference: U.S. Pat. No. 5,158,084 to Ghiatas, U.S. Pat. No. 5,409,004 to Sloan, U.S. Pat. No. 5,059,197 to Urie et al., U.S. Pat. No. 5,197,482 to Rank, U.S. Pat. No. 5,221,269 to Miller et al., and U.S. Pat. No. 4,592,356 to Gutierrez. Other devices such as that described in U.S. Pat. No. 5,989,265 to Bouquet De La Joliniere et al. and U.S. Pat. No. 5,709,697 to Ratcliff et al., each incorporated herein by reference, are directed to similar devices.
Despite the advantages of wire localization techniques to locate the suspect tissue for the surgeon, they have a number of severe limitations.
Such wires are often inaccurately placed and they cannot be removed except by surgical excision. For these reasons, the radiologist must mark the x-ray film or prepare notations providing instructions to the surgeon on how to find the lesion as a backup to confirm the proper location of the needle.
Because the distal tip of the wire might have been placed anywhere from the very center of the lesion to quite some distance away from the lesion, the surgeon must guide a scalpel along the wire and rely upon the skill of the radiologist and the marked x-ray film in the excision procedure. Even if the wire has been properly placed in the lesion and the x-ray film clearly shows the lesion boundary or margin, the surgeon often cannot see the tip of the wire (given the surrounding tissue) so she must remove a larger portion of tissue than is necessary to ensure proper excision.
If the lesion is not found at the end of the wire, the surgeon ends up cutting or removing non-afflicted tissue without removing the lesion. Also, if the tip of the wire penetrates the lesion, the surgeon may sever the lesion in cutting through the tissue along the wire to reach its end. In the latter case, a re-excision may be necessary to remove the entire lesion. Over twenty-five percent of wire localization procedures require re-excision. Post-excision re-imaging is almost always performed prior to closing the surgical field to ensure that the targeted tissue volume containing the suspect lesion is removed.
When marking lesions in the breast, two paddles are typically used to compress and stabilize the breast for placement of the wire. Upon release of the breast from compression, the wire marker can dislodge or migrate to another position away from the suspect tissue. It may also migrate while the patient awaits surgery. In addition, the fact that the breast is in an uncompressed state for the excision procedure renders a different view of the lesion with respect to the healthy tissue.
Various tissue localization systems have been developed to minimize inadvertent migration of the wire by configuring the wire with a bend or hook, such as Ghiatas et al., discussed above, U.S. Pat. No. 5,011,473 to Gatturna, and the MAMMALOK needle/wire localizer sold by Mitek Surgical Products, Inc., Dedham, Mass. Even if a wire does not migrate after placement, the surgeon cannot determine the shortest path to the lesion; rather, the surgeon must always follow the wire, which is rarely the more cosmetically desirable path to the lesion (such as a circumareolar approach).
Because the distal tip of the wire is often placed in the center of the suspect tissue, a problem known as xe2x80x9ctrack seedingxe2x80x9d can occur in which possible cancerous or precancerous cells are disturbed by the wire and are distributed to unaffected tissue during the procedure.
Aside from the above concerns, the use of a localization wire marker presents logistical problems. After placement, the wire protrudes from the body. It is almost always necessary for the patient to proceed with the surgical removal of the lesion immediately after wire placement to minimize the chance of infection, wire breakage or disturbance, etc. However, delays between placement of the wire and eventual excision often can exceed several hours.
Furthermore, conventional tissue locators tend to be difficult to deploy in areas where there is scar tissue, calcified tissues, or particularly dense tissues. The locator element or wiring that is inserted into the tissue tends to be blocked by scar tissue and other hardened tissues. It is highly desirable to have an effective means to facilitate the insertion of a locator element by minimizing resistance due to calcified tissue and other hardened tissues.
What is needed is a tissue-locating device that may be smoothly inserted into the subject to surround a volume of interested tissue with minimal effort and maximum precision. Such a device should reliably define the border of the volume of tissue to be removed without the risk of self or inadvertent migration. The device should also provide a surface against which the surgeon may reliably cut when excising the tissue. Furthermore, a need remains to improve the interaction between the radiologist and surgeon, eliminate the need for post-excision x-rays and re-excision, reduce the overall time for the procedure, and allow a surgeon to select the shortest or most cosmetically desirable path to the suspect tissue.
The present invention relates to a tissue-localizing device with an energized locator element and methods for its use. The tissue-localizing device includes a locator element adapted to penetrate tissue so that the distal portion of the locator element forms at least a partial loop that defines a volume of tissue when the locator element is deployed in a mammalian body. The locator element, when deployed, may define a volume of tissue for subsequent excision and contains a target region that may contain a lesion, foreign object, one or more microcalcifications, or a palpable or nonpalpable mass. This tissue volume is substantially bounded but preferably not penetrated by the locator element. The locator element may be adapted to form a partial or complete loop around a target region having a diameter as small as three millimeter. It is preferable that the loop formed by the locator element has a diameter in the range of about three millimeter to about ten centimeter. It is even more preferable that the diameter of the loop be within the range of about five millimeter to about five centimeter. When deployed, manipulation of a proximal portion of the locator element may result in a corresponding direct or proportional manipulation of the tissue volume it bounds.
The conductive locator element may be configured for delivering a current or an electromagnetic field depending on the particular application. For example, the locator element may be configured as an electrode to carry alternating current of various radio frequencies. In this application, a second electrode or conductive member may be adapted to complete the current loop so that current may flow from the locator element to this secondary electrode or conductive member. Alternatively, the locator element may be configured as an antenna to deliver electromagnetic field to the localized tissue. The electromagnetic field is generated when an alternating current is inputted to the antenna.
It is preferable that alternating current within the radio frequency (RF) spectrum is used to energize the locator element or a conductive region on the locator element. It is more preferable that the energizing current carries a frequency or frequencies within the range of about three kilohertz to about three hundred gigahertz. The power supply may have an alternating current output power within a range of zero to about four hundred watts. For RF ablation applications, it is more preferable that the primary RF frequency is within about ten kilohertz to about one hundred megahertz. It is even more preferable that in RF ablation application that the primary RF frequency be within about one hundred kilohertz to about one megahertz. For ultrasound applications, it is more preferable that the locator element is energized with a current carrying at least a frequency within the range of about ten kilohertz to about fifty megahertz. It is even more preferable that in ultrasound application the frequency be within the range of about five hundred kilohertz to about ten megahertz. For microwave applications, it is more preferable that the locator element is energized with a current carrying at least a frequency within the range of about one hundred megahertz to about three hundred gigahertz. It is even more preferable that in microwave application the frequency be within the range of about three hundred megahertz to about three gigahertz.
The RF energized locator element may be used to facilitate the deployment of the locator element. Alternatively, the energized locator element may be used to deliver RF current or RF electromagnetic wave to a localized region of tissue for therapeutic or medical intervention purposes.
Preferably the locator element is at least partially radiopaque ribbon with one or more optional cutting surfaces. The locator element also preferably exhibits shape memory characteristics. Alternatively, the locator element may be plastically deformed to take an arcuate or curvilinear shape during deployment through a die.
The locator element is adapted to penetrate tissue so that at least part of the distal portion of the locator element forms a partial loop that defines a volume of tissue. The locator element defines a volume of tissue that may be subsequently excised along the boundary defined by the locator element.
The locator element is preferably electric conductive. Various metals and metal alloys that are highly conductive may be used to construct the locator element. The locator element may also be at least partially electrically insulated with a coating of insulating material, such as a polymer coating, on one or more sides of the locator element. The insulating layer may be biocompatible plastics such as parylene, polyethylene, polypropylene, polyvinylchloride (PVC), ethylvinylacetate (EVA), polyethyleneterephthalate (PET), polyurethanes, polycarbonates, polyamide (such as the Nylons), silicone elastomers, fluoropolymers (such as Teflon(trademark)), and their mixtures and block or random copolymers may be applied as an insulating layer and/or as a protective coating. This insulative material may have a low coefficient of friction for ease of entry into the tissue. Alternatively, the electric insulation may also be achieved through placement of a heat-shrink tubing over the locator element. Preferably the distal end of the locator element is exposed to provide a path for delivery of electric energy to the tissue.
Alternatively, the locator element may be constructed with a non-conductive material, such as super elastic polymer, and a conductive member is then adapted to the body of the locator element to provide the means for electric conduction. Conductive regions may also be established on a locator element through electroplating, electrodepostition or plasma deposition of conductive materials, such as copper, chromium, silver or gold.
Alternatively, the locator element has two or more conductive regions. In one variation, the plurality of conductive regions is constructed on the surface of the locator element through adaptation of two independent conductive members, such as metal wires with high conductivity, to the locator element. It may also be possible to fabricate the two electrodes on the surface of the locator element through deposition of conductive materials, such as copper, chrome, silver, gold or metal alloys, on the surface of the locator element. Two or more surfaces that are electrically isolated from each other may be deposited on the surface of the conductor element through plasma thin film deposition, electroplating or electrodeposition. Alternatively, a plurality of electrodes may be fabricated on the locator element through placement of multiple layers of conductive materials that are electrically insulated from each other. For example, on top of a locator element constructed of metal alloy, an insulating layer, such as polyamide or other polymers with low conductivity, maybe deposited on its surface, and a layer of conductive material may be deposited on top of the insulating material to serve as the second electrode. A second layer of polymer may be deposited on top of the conductive layer to alter the amount of the conductive area exposed. If necessary, additional layers of conductive materials and polymer may be deposited to create additional electrodes as needed. The independent conductive regions may be selectively implemented as the active and return electrodes in a bipolar electric energizing configuration.
In another variation, one or more electric conductive member may be adapted or coupled to the locator element. If the locator element is also conductive, an insulating layer may be provided to separate the conducting member from the locator element. The conductive member may be comprised of metal wires or electrodes, metal alloy wires or electrodes, and other electric conductive wiring and medium well known to one skilled in the art.
The tissue-localizing device may also include a sleeve that is placed over the locator element. The locator element is slidably positioned within the lumen of the sleeve. The sleeve may be used to penetrate the target tissue. The sleeve may be flexible, semi-flexible or rigid depending on the particular application. Alternatively, the sleeve may comprise a cannula. The distal end of the sleeve may have a sharp edge to facilitate penetration of the tissue.
A locking mechanism may also be provided to temporarily secure the position of the locator element relative to the sleeve. When the locator element is secured by the locking mechanism the sleeve and the locking mechanism may be advanced into the tissue as a single unit.
The sleeve may also be electric conductive. For example, the sleeve may be comprised of a metal cannula. An insulating layer may be placed over the sleeve exposing only the distal end of the sleeve. Alternatively, metal deposition techniques well known to one skilled in the art may be applied to establish a conductive region on the sleeve. It is preferable, but not necessary, that the conductive region be on the distal end of the sleeve. The conductive sleeve may also be energized to facilitate the penetration of the sleeve into the tissue. Alternatively, the conductive sleeve may provide a return pathway for electric current in a bipolar electric configuration.
The sleeve may additionally comprise a cold forming die at the distal end of the sleeve that is adapted to plastically deform the locator element into an arcuate shape. The die may include a reverse curve and a positive curve for shaping the locator element, and it may also comprise an axially adjustable upper portion connected to a lower portion.
A power supply may be connected to the locator element for delivering electric energy to the conducting surface on the locator element. The power supply may be able to deliver a current with a particular frequency within the range from about three kilohertz to about three hundred gigahertz. Alternatively the power supply may have a variable current output with a frequency range within the three kilohertz to three hundred gigahertz range. Various RF, microwave, and ultrasound generators well known to one skilled in the art may be adapted to provide the electric energy to the locator element. In another variation, the power supply may deliver a DC current to the to the locator element.
The power supply and the tissue-localizing device may be configured to deliver electric energy to tissue. The system may be specifically configured for delivering RF ablation current, microwave energy, ultrasound energy, and other electric energy that are well known to one skilled in the art. As described above, the electric energy is preferably delivered to the target region as an electric current, but it may also be delivered to the target region as an electromagnetic wave.
The delivery of energy may be achieved through monopolar or bipolar configurations. In a monopolar configuration, the locator element preferably serves as the primary electrode deliverying the electric energy. In applications where the primary electrode is used to delivery a current to the tissue, a secondary electrode or conductive pad may be place on the subject to provide a return path for the current to flow back to the power supply. In an alternative arrangement, the locator element may serve as the secondary or ground electrode, and a separate electrode or conductor is placed at a separate location on the subject to complete the electric loop.
The monoplar configuration may be achieved through implementation of a locator element with an electric conductive surface. In one variation, the power supply is electrically connected to a conductive path that connects to the conductive surface on the locator element. An electric conductive pad is secured to the surface of the subject""s body and a separate electric conductive path connects the pad to the negative or ground connection on the power supply to complete the electric current loop.
In a monopolar configuration, it may also be possible to direct the current down the sleeve of the tissue-localizing device to facilitate the insertion of the sleeve into the tissue. Once the sleeve is in position, a current may be directed down the locator element to facilitate the deployment of the locator element. In one variation, the same current source is used to charge the sleeve and the locator element. A current switch may be incorporated to selectively direct current down the sleeve and/or the locator element.
In the bipolar configuration, it is preferable that the locator element serve as the primary electrode and the sleeve serve as the secondary electrode. It is also possible to use a locator element with two or more separate conductive regions. In such a case, both the positive and negative electrodes for the bipolar system may be located on the locator element.
The power supply may be integrated with the tissue-localizing device as one unit or it may stand as a separate unit connected to the tissue-localizing device. The power supply may deliver DC and/or AC current depending on the particular application. Integrated circuit based switching and controlling circuits may be implemented to manufacture a miniature power control unit that can easily be integrated into a handle that is attached to the sleeve and the locator element. In some applications, a separate unit containing the power supply and control circuit may be preferable in order to minimize the production cost of the system or to implement a more sophisticated feed back control mechanism that is capable of monitoring physiological changes and modulate the ablation current during the insertion of the tissue-localizing device.
A temperature sensor may also be adapted or coupled to the tissue-localizing device for monitoring local tissue temperature fluctuation. This may be particularly useful in applications where RF energy is used for ablating tissue around the locator element. The temperature sensor allows for monitoring of local tissue temperature to guard against over heating of tissue. A close loop control mechanism, such as a feedback controller with a microprocessor, may be implemented for controlling the delivery of RF energy to the target tissue based on temperature measured by the temperature sensor.
The temperature sensor may be coupled or adapted to the locator element, or alternatively coupled or adapted to the sleeve of the tissue-localizing device. Miniature sensors well known to one skill in the art and suitable for this particular in vivo application may also be used. For example, thermal couples, thermistors, and various semiconductor based temperature sensors may be implemented on the tissue-localizing device.
This invention is also a method for placing a removable locator element in tissue. This method is accomplished by inserting a sleeve containing a locator element slideably positioned within a lumen of the sleeve at a position adjacent the targeted tissue, and advancing a locator element through a distal end of the sleeve and penetrating tissue so that at least a portion of the locator element forms a partial loop around the target tissue. The deployed locator element defines a volume of tissue for subsequent treatment or excision. The tissue volume will contain a target region that is substantially bounded but not penetrated by the locator element.
The sleeve and/or the locator element may be energized with RF energy to facilitate the penetration of the sleeve/locator-element unit into the tissue. The RF energy may be delivered simultaneously while the sleeve/locator-element is being advanced into the tissue, or alternately by energizing the locator element in between intermitted pressure applied to advance the locator element into the tissue.
Alternatively, the invention is a method for excising a volume of tissue that comprises advancing a locator element with the assistance of RF energy through tissue to define a volume of tissue to be excised, and cutting tissue substantially along a surface of the locator element immediately adjacent the tissue volume. Rotation of the locator element or elements through an angular displacement, to facilitate cutting through tissue to remove the tissue volume is also feasible. RF energy may also be applied, intermittently or continuously, to the locator element to facilitate the excision of the target tissue.
Preferably, the device is palpable when in position around the tissue volume. Tissue may be penetrated through any excision path to the tissue volume as the surgeon sees fit. For instance, the surgeon may cut down along the locator element extension wire, or, when the device is disposed in breast tissue, circumareolarly.
The locator element may be proximally withdrawn from the tissue after it is advanced to define the tissue border for eventual re-advancement through the distal end of the deployment sleeve or complete removal from the body.
The locator element may be placed under x-ray guidance, stereotactic x-ray guidance, ultrasonic guidance, magnetic resonance imaging guidance, and the like. Target region visibility may be enhanced by, e.g., the placement or injection of an echogenic substance, such as collagen, hydrogels, microspheres, microbbules, or other like biocompatible materials, or by the injection of air or other biocompatible gases or contrast agents.
The tissue-localizing device with an energizable locator element may also be utilized for local activation of drug, medication or chemicals. An inactivated chemical may be injected into the body of the subject. The drug diffuses in the subject""s body through the circulatory system. The locator element is deployed around the target tissue. Delivery of RF energy, microwave or ultrasound may activate the chemical locally around the target region. The chemicals may be activated by direct RF energy due to the chemicals entering the RF energy field, or it may be activated due to the elevated temperature in the local tissue exposed to the RF energy. Alternatively, it may also be possible to activate drugs or chemicals with RF current.
Variations of the invention may also include a tissue locator element pusher assembly. The pusher assembly is adapted to the sleeve and the locator element. A pusher within the pusher assembly may be adapted to control the sliding action of the locator element along the lumen of the sleeve. An adjustable fastener for slidably fixing a portion of a tissue locator element to the pusher may also be included. A deployment fixture may be detachably affixed to a distal end of the locator element. The locator element may be released and separated from the pusher assembly.
Alternatively, the tissue locator element pusher assembly may include a housing having a lumen, a pusher having a pusher lumen slidably disposed in the housing lumen, a tissue locator element at least partially disposed in the pusher lumen, and a delivery tube or sleeve having an optional sharpened distal tip and affixed to the housing. The delivery tube or sleeve has a lumen adapted for slidably receiving the pusher and the tissue locator element.
Still further, the tissue locator element pusher assembly may include a housing having a proximal end, a distal end, a central housing lumen, and at least one longitudinal slot in communication with the housing lumen, and a pusher slidably disposed in the housing lumen. The pusher may have a pusher lumen and an adjustable fastener for slidably fixing a portion of a tissue locator element to the pusher, a control lever affixed to the pusher and extending at least partially through the housing slot, and a tissue locator element at least partially disposed in the pusher lumen. A delivery tube or sleeve may have a lumen adapted for slidably receiving the pusher, and the locator element may be disposed on the distal end of the housing in communication with the housing lumen.
Further, this pusher assembly may be configured so that axial movement of the control lever will result in a corresponding axial movement of the pusher and the locator element. In this way, the locator element will reversibly extend through an aperture in a distal end of the delivery tube. The assembly may also be set up so that sufficient axial movement of the control lever may cause it to engage a detent disposed in the housing, prohibiting substantial further axial movement of the control lever. The engagement of the control lever and the detent may be configured to correlate to an extension of the locator element shoulder through the delivery tube distal end aperture. The assembly may further be set up so that just prior to engaging the detent, tactile or other feedback is provided to indicate that the engagement point is about to be reached.
Furthermore, the tissue localizing system may include electronic controller that is adapted to modulate the RF current delivered to the locator element. The controller may be integrated with the pusher assembly or it may be integrated with the power supply. Alternatively, the controller may be a separate unit connected to the power supply and the pusher assembly. The controller may be adapted to energize the locator element when a pressure is applied to advance the locator element forward. Alternatively, the power controller may be adapted to respond to a control switch that is located on the pusher assembly or as a separate unit that is in communication with the controller. In another variation, the controller may only energize the locator element when the locator element experiences a resistance that is above a predefined threshold during the deployment process.
The sleeve of the tissue-localizing device may be adapted for delivery of fluids, chemicals or drug into the tissue. A delivery port and a fluid communication channel connecting the port to the lumen of the sleeve may be integrated into the pusher assembly to facilitate the delivering fluid to the tissue via the sleeve of the tissue-localizing device.
Although the tissue locator element is primarily intended to mark a volume of tissue without penetrating it, the tissue locator element may be used as a tissue localization wire in which at least a portion of a tissue volume (which may or may not include a lesion) is penetrated to mark it for later excision.